The commercial rooftop solar energy market remains an under-developed sector. The market is estimated to contain 150 gigawatts of potential in the U.S. but it faces significant barriers to deployment to meet that potential, with an estimated 1.4 GW developed through 2017. This analysis focuses on of over 30,000 solar systems installed through 2017 and the properties on which they are located. The sample represents greater than 60% of the installed market at that time. The properties covered 20 states and almost 30 different types including industrial, warehouse, school/university, office, retail, and municipal/government and were compared to more than 2.4 million non-solar properties in the same geographies. The analysis finds overall commercial rooftop PV penetrations have only surpassed 1% recently across all property types with education properties (schools and universities) leading at over 6% penetration and with NJ and CA seeing the highest overall penetrations close to 2.5%. Also revealed were characteristics of those buildings, owners, and tenants and how solar penetrations change as those characteristics change. The research found clearly higher penetrations on owner-occupied larger (>9000 ft2) buildings with fewer tenants indicating, potentially, areas for future customer acquisition for PV developers. Also investigated were differences of solar system characteristics on commercial buildings such as system installed prices, size, and percentages of third-party owned (TPO) systems. The research found a steady and substantial drop in installed prices over time, a drop in the percentage of TPO systems being installed, and a relatively steady trend of system size. This latter finding indicates that smaller systems remain difficult to develop.